Early Intel iMac (Model A1208 EMC 2114) Hard Drive Replacement
5 - 15 minuten
The hard drive failed.
The repair went well. It took a little less than three hours, but I did it at a leisurely pace. The instructions were very good and easy to follow. I could not imagine trying to do this only with the guidance you see in online videos.
If you have an iMac this old, I would not wait until it finally becomes obvious that the hard drive has failed. It is probably starting to fail now and you don't understand the problems you are having with your machine are caused by this slow degradation. I put up with three months of weirdness from my iMac ending with several attempts to reinstall the OS before Disk Utility told me the truth: the hard drive was beyond repair. The S.M.A.R.T. status can lie, lie, lie, like nothing else.
Before you start, pick up a CR2032 battery to replace the PRAM battery, which, like the hard drive, will be at the end of its life too. The spudger is useful for removing the old battery. I had a little Torx kit already, but I would recommend getting the long T-10 driver. It really would be a serious pain-in-the-*** to have to pick your disassembled iMac up to shake out a dropped screw.
I ended up getting a performance bump because not only was my iMac not acting strangely (failure to respond to right mouse-clicks, spinning beach balls with even the simplest of commands etc.), but with a much bigger drive, I was able to put all my photos and music on my iMac (instead of many external drives).
After installing the new hard drive and when you are installing OS X, only set up a bare bones admin-level account that does not use your name (you can import your account after OS X is up to date later with Applications>Utilities>Migration Assistant). After you get OS X installed, immediately turn on the firewall (System Preferences>Security>Firewall) and turn off Java (System Preferences>Applications>Utilities>Java Preferences). Then use >System Update to get the updates you need to bring your OS X up to date, but instead of letting System Update run the show (this does not always work well for Snow Leopard), use the items in System Update to do a web search to the Apple web page that will allow you to download the update, for example: "Apple Mac OS X Security Update 1.2.3." This way you can have the update right on your machine so to make subsequent re-installations of Mac OS X go much faster (I did this more often than I thought because after you see the options available in Migration Assistant, you may elect to create a "cleaner" install). I now have a DVD with all the necessary updates to Snow Leopard right with the Snow Leopard install disc. Also on the DVD are install files for apps I commonly use like Chrome, Audacity, and Skype should they decide to not provide these for Snow Leopard at some time in the future.
Have fun giving your iMac many more years of functionality. After Apple no longer supports my iMac security-wise, it will still be part of my entertainment center (I have several AirPort Expresses that make a whole-house music system) and I will lock it down so that it can only access the internet for radio streaming etc.